The initial impetus for the present invention, and a major object of the present invention, is a coupler between a ground or floor mounted anchoring stub-post and a vertically-extending post that supports a mail-box or other object. The present invention strives to abate the perennial problem of rural type mail-boxes (or buffers and supports used in warehouses or the like) being knocked down by an errant vehicle and then requiring a major effort to be resurrected. Additionally, the present invention can add safety to sports by disconnecting basketball hoops and hockey nets before injury can occur, and add safety to shovels or drawbars by disconnecting excessive loads.
Many mechanical couplers exist that decouple at a particular applied moment with the breaking of something. The term "break-away" is frequently applied to such couplers. Some of these couplers may be recoupled when the part broken during decoupling is replaced. A representative U.S. Patent showing this type of device is U.S. Pat. No. 4,021,977 to Deike. The Deike patent places a plastic pipe inside of, and bridging, two coaxial posts such that the plastic pipe will break when the assembly is struck. Extra length of plastic pipe is provided so that a fractured portion may be discarded, a weakening hole pierced in the remainder, and the remainder used as the next weak link. It is a major object of the present invention to provide a coupling that does not break anything incident to decoupling and that is readably recoupled after a decoupling.
In some applications of decoupling couplers the direction of the relevant force may be predicted. A sign post placed next to the edge of a road is most likely to be struck by a blow that is roughly parallel to the road. Couplers having a decoupling moment that is a significant function of the azimuth of the applied force are known. A representative U.S. Patent describing this type of device is U.S. Pat No. 4,171,919 to Willis. The device disclosed in Willis involves interposing a "retaining member" having a long axis between the ends of two coupled posts. The relevant ends of the posts are formed into identical, elaborate tongue-and-groove fittings having a void that runs normal to the major axis of the posts. The retaining member is placed within the void with its long axis normal to the major axis of the posts. The moment required to decouple this device must vary significantly with the azimuth of the applied force. It is also disclosed that the retaining member is expected to be replaced after it is destroyed. Many applications exist (such as buffers or supports in a warehouse or the like) where the decoupling force might arrive from most any azimuth. Therefore, an additional object of the present invention is to provide a coupling with a decoupling moment that is substantially independent of the azimuth of the applied force.
It is a major object of the present invention to provide a coupling that has a decoupling moment that is adjustable. It is preferable that the decoupling moment be adjustable manually by a human without the use of tools. Secondarily, it is desirable that the decoupling moment be adjustable at the time of manufacture.
It is a major object of the present invention to provide a coupling that is easy for a human to couple, or to recouple if decoupling has taken place, without the use of tools and only using the original parts of the coupler. In this context, "easy" means an effort that is both not significant for an average adult human and an effort that is much less than the effort needed to decouple the coupler. Effort includes moment.
It is a major object of the present invention to provide a coupling that requires less moment to adjust the decoupling moment than the resultant decoupling moment when the decoupling moment is manually adjusted.